Process for producing a non-combustible moulded article, especially a building panel

ABSTRACT

A process is proposed for producing non-combustible moulded articles from blown vermiculite, the blown vermiculite granules being mixed with an inorganic binder and then pressed. The blown vermiculite granules are mixed with a solution of an inorganic binder, the vermiculite granules once mixed are pre-pressed, cut to the shape required and the cut blanks are pressed non-continuously at at least room temperature and preferably at temperatures of at least 100° C. and pressures of at least 0.3 N/mm 2  to ensure that all solvent residues are removed from the finished noncombustible moulded article.

TECHNICAL AREA

[0001] The invention relates to a process for the production of nonflammable molded parts, especially building material panels, in which vermiculite granules are expanded at an elevated temperature and then mixed with a binding agent, following which a bulk material or compressed cake is formed of the granulate, which has been coated with adhesive, and it is pressed into a nonflammable molded part.

STATE OF THE ART

[0002] In the production of nonflammable molded parts, it is known how to coat expanded materials such as vermiculite, perlite, or light expanded clay aggregate with binding agents comprised of inorganic and organic components, and then to compress them so that a connection of the expanded material particles to each other arises. Due to the fact that condensation resins, such as formaldehyde condensation resins, for example, are used as organic components, it has been shown that, due to the processing parameters during the compression procedure, compounds of these resins that have a low molecular weight, such as formaldehyde, are liberated. As a result, these well-known methods have proven to be a relatively large source of environmental pollution.

[0003] Now it is the task of the invention to indicate a process of the type mentioned at the outset for the production of nonflammable molded parts that is environmentally friendly and yields satisfactory properties at the end product of the process, such as its mechanical stability and absence of flammability.

PRESENTATION OF THE INVENTION

[0004] According to the invention, therefore, a process of the type mentioned at the outset is proposed, which is characterized by the fact that the expanded vermiculite granulate is furnished with an application of an adhesive coating comprised of a solution of an inorganic binding agent, and that the coated vermiculite granulate is precompressed, continuously or discontinuously, cut to the shape of the individual piece, and that these custom-cut pieces are compressed discontinuously at room temperature or higher, preferably at temperatures of at least 100° C., and at pressures of at least 0.3 N/mm², so that all solvent residues are removed from the final, finished, nonflammable molded part.

[0005] An advantage of the process according to the invention resides in the fact that the discontinuous hot compression occurs in a press that is heated by the usual heating media, and by means of high-frequency current as well. Furthermore, the discontinuous hot compression occurs, to good advantage, in the presence of a steam sieve for the purpose of removing solvent residues. Similarly, in the case of the continuous precompression, cover sheets arranged on one or both sides of the bulk cake can be compressed with the cake to good effect.

[0006] In the process according to the invention, a binding agent that contains phosphorous is used to good advantage as an inorganic binding agent, such that those that are based upon acids that contain phosphorous, and/or their salts, are particularly well-suited.

[0007] Furthermore, silicate compounds can be used to good effect as inorganic binding agents, preferably silicate of potassium or sodium, hydraulic binders, preferably cement, Sorel binders, as well as hemihydratic or hydratic binders, such as gypsum. Other additives, preferably agents that render the solution hydrophobic, may be added to the solution of inorganic binding agents as well.

AN ADVANTAGEOUS WAY OF IMPLEMENTING THE INVENTION

[0008] The invention will now be illustrated in greater detail by virtue of an embodiment example:

[0009] In a rotary kiln, the vermiculite granulate is expanded at a temperature of ca. 850° C. The expanded vermiculite granulate is then placed into a mixing unit, in which it is mixed with the binding agent solution, which is added by means of a dosage apparatus. The binding agent solution consists, for example, of aqueous orthophosphoric acid, which contains, in addition, hydrophobizing agents that are based upon organo-silicon compounds. The dosage is controlled in such a manner that the quantity of binding agent in the finished panel amounts to about 10% by weight.

[0010] The mixture that is removed from the mixing unit, which has been given an adhesive coating of binding agent, is now transferred to a dispersion hopper or a dispersion station, in which a bulk load of uniform height is formed. This bulk load is then transported to a preliminary compression unit in which it undergoes precompression to about 50% of the original bulk load's height. Covering sheets, such as decorative sheets, can be applied to both sides of the bulk cake. After the preliminary compression, the blank that has undergone preliminary compression is cut into large panels and transferred discontinuously to a press that can be heated with high-frequency current and heating oil, in which the panels are compressed at a temperature of 200° C. and a compression pressure of 1 N/mm². A cross-linking of the phosphoric acid, with a loss of water, occurs as a result of the elevated temperature. This water from the reaction, as well as any solvent residues that may be present, can be removed by means of a steam sieve that is applied within the press. As a result of this measure, irregularities in the surface of the panel can be avoided. The finished pressed panel is now separated from the pressure panel and cooled. Then the panels are cut to the desired format and stacked.

COMMERCIAL APPLICABILITY

[0011] The nonflammable molded parts that are manufactured according to the invention can be used, for example, in machine building and in the construction industry. 

1. A process for the production of a nonflammable molded part, in particular, a building material panel, in which vermiculite granulate is expanded at an elevated temperature and then mixed with a binding agent, following which a bulk load or a compressed cake is formed of the granulate that has been coated with adhesive and pressed into a nonflammable molded part, characterized by the fact that a coating of adhesive solution of an inorganic binding agent is applied to the expanded vermiculite granulate, that the vermiculite granulate that is furnished with the adhesive coating is subjected to preliminary compression, continuously or discontinuously, custom cut to the individual shape of the piece, and that these custom-cut units undergo discontinuous compression at room temperature or higher, preferably at temperatures of at least 100° C., and pressures of at least 0.3 N/mm², so that all solvent residues are removed from the finished, nonflammable molded part.
 2. A process according to claim 1 , characterized by the fact that the discontinuous hot compression occurs in a press that is heated with the usual heating media, and in addition by means of high-frequency current.
 3. A process according to claim 1 or 2 , characterized by the fact that the discontinuous hot compression occurs in the presence of a steam sieve in order to remove solvent residues.
 4. A process according to one of claims 1 through 3, characterized by the fact that in the case of the continuous preliminary compression, covering sheets that are provided on one or both sides of the bulk cake are compressed as well.
 5. A process according to one of claims 1 through 4, characterized by the fact that the inorganic binding agent is a binding agent that contains phosphorous.
 6. A process according to claim 5 , characterized by the fact that the inorganic binding agent that contains phosphorous is one that is based upon acids that contain phosphorous and/or their salts.
 7. A process according to one of claims 1 through 4, characterized by the fact that the inorganic binding agent is one based upon silicate compounds, preferably silicate of potassium or sodium.
 8. A process according to one of claims 1 through 4, characterized by the fact that the inorganic binding agent is a hydraulic binder, preferably cement.
 9. A process according to one of claims 1 through 4, characterized by the fact that the inorganic binding agent is a Sorel binder.
 10. A process according to one of claims 1 through 4, characterized by the fact that the inorganic binding agent is a hemihydratic or hydratic binder, such as gypsum.
 11. A process according to one of claims 1 through 10, characterized by the fact that additives, preferably hydrophobizing agents, are mixed with the solution of inorganic binding agents. 